不需要2次 setContentView(tv); public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        TextView tv=new TextView(this);        
        setContentView(tv);
        Thread t=new Thread();
        t.start();
        try {
            tv.setText("hello");
            Thread.sleep(5000);
            tv.setText("world");
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        t=null;
    }试试